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The zygote is the earliest developmental stage. In humans and most other anisogamous organisms, a zygote is formed when an egg cell and sperm cell come together to create a new unique organism. The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming.
The embryo is joined to the trophoblastic shell by a narrow connecting stalk that develops into the umbilical cord to attach the placenta to the embryo. [ 11 ] [ 15 ] Arteries in the decidua are remodelled to increase the maternal blood flow into the intervillous spaces of the placenta, allowing gas exchange and the transfer of nutrients to the ...
The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a fruit, which surrounds the seed(s).
The zygote contains a full complement of genetic material with all the biological characteristics of a single human being, and develops into the embryo. Embryonic development has four stages: the morula stage, the blastula stage, the gastrula stage, and the neurula stage. Prior to implantation, the embryo remains in a protein shell, the zona ...
During sexual intercourse, sperm cells are ejaculated into the vagina through the penis, resulting in fertilization of an ovum to form a zygote. [1] While normal cells contain 46 chromosomes (23 pairs), gamete cells contain only half that number, and it is when these two cells merge into one combined zygote cell that genetic recombination occurs.
Fertilization was not understood in antiquity. Hippocrates believed that the embryo was the product of male semen and a female factor. Aristotle held that only male semen gave rise to an embryo, while the female only provided a place for the embryo to develop, [5] a concept he acquired from the preformationist Pythagoras.
The zygote undergoes a series of cell divisions (called cleavage) to form a structure called a morula. The morula develops into a structure called a blastula through a process called blastulation. The blastula develops into a structure called a gastrula through a process called gastrulation. The gastrula then undergoes further development ...
The division of blastomeres from the zygote allows a single fertile cell to continue to cleave and differentiate until a blastocyst forms. The differentiation of the blastomere allows for the development of two distinct cell populations: the inner cell mass, which becomes the precursor to the embryo, and the trophectoderm, which becomes the precursor to the placenta.